Corrosion in cracked and uncracked concrete – influence of crack width, concrete quality and crack reopening

Abstract

Cracks influence the durability of reinforced concrete (RC) structures in aggressive environments by accelerating the ingress of corrosive agents to the embedded steel. This study investigated the influence of crack width (0 . 7 mm, 0 . 4 mm and incipient cracks), binder type (100% CEM I (ordinary Portland cement -OPC) and 50/50 OPC/Corex slag blend), water-to-binder (w/b) ratio (0 . 40 and 0 . 55) and crack reopening on chloride-induced corrosion in RC specimens with constant cover of 40 mm. Over the study period (31 weeks), corrosion rates varied from passive values of 0 . 01 ìA/cm 2 to active values of 1 . 50 ìA/cm 2 . Results indicate that corrosion rate is sensitive to crack width, concrete quality (i.e. binder type and w/b ratio) and crack reopening. For a given binder type and w/b ratio, corrosion rate increased with increasing crack width; however, this increase was smaller in Corex slag specimens (increases of 40% or more) than in OPC specimens (increases 210% or more). Corex slag specimens generally had lower corrosion rates compared to OPC specimens. For both OPC and Corex slag specimens, corrosion rate decreased with decreasing w/b ratio. Crack reopening increased the corrosion rate in the cracked specimens. This increase in corrosion rate was higher if the specimen was actively corroding prior to the crack reopening.

Characterisation of bending cracks in R/FRC using image analysis

“…Although a correlation does not seem to exist between the crack width in concrete and the corrosion rate of embedded reinforcement in the long term [4,5,6], a relation has been observed between crack width and corrosion rate at early stages [7]. Most of the available research investigating the relation between crack width and corrosion is, however, based on cracks measured at the surface, which are greatly dependent on the cover depth.…”

Influence of Micro and Macro Cracks Due to Sustained Loading on Chloride-Induced Corrosion of Reinforced Concrete Beams

“…Given that all these beams were saturated with chloride solution at the time of measurement, this cannot be assigned to the variations in moisture content. However, it has been demonstrated by Sahmaran (2007) and Otieno et al (2010) that self-healing phenomenon of small cracks can improve the corrosion resistance with time. This effect could be seen in beams subjected to both levels of loading (Figure 6), though for beams that were not subjected to 50% of F 0.1 , the effect was smaller.…”

“…However, most of them investigated the corrosion of steel in 'lab concrete', which was uncracked and not subjected to any structural loads (Bamforth, 2004;Violetta, 2002;Thomas & Bentz, 2001;Siemes & Edvardsen, 1999). Although a small proportion of them dealt with chloride induced corrosion in cracked concretes, the influence of cracks wider than 0.07 mm, or even sometimes wider than 0.7 mm, termed commonly as macro-cracks, was investigated (Sangoju et al, 2011;Otieno et al, 2008& 2010, Sahmaran, 2007Rodriguez & Hooton, 2003;Mohammed et al, 2001;Schiessl & Raupach, 1997). In fact, the maximum crack width allowed in designing reinforced concrete is 0.3 mm in chloride-laden environment according to BS EN 1992-1-1:2004(British Standards Institution, 2011a.…”

Effect of Steel Fiber and Different Environments on Flexural Behavior of Reinforced Concrete Beams

“…The main kind of deterioration in marine RC structures is steel bar corrosion due to chloride ion penetration. During the service life of marine structures, concrete cracking can facilitate the chloride penetration and increase the steel bar corrosion [2]. To reduce the concrete cracking, fibers can delay the start and growth of the cracks.…”